1. Field of the Invention
The present invention relates to a printing group cylinder of a web-fed rotary printing machine and, more particularly, to the mounting of form cylinders and transfer cylinders in a printing machine so as to obtain good print quality.
2. Description of the Related Art
In web-fed rotary printing machines, there must be a constant line force between the cylinders printing the web to attain good print quality. Constant adjustment forces are also necessary between the form cylinder and the transfer cylinder. In order to fulfill this condition, the axial distance between the cylinders positioned against one another must always be the same. German Patent No. DE-OS 2614792 describes a printing machine in which the cylinders are equipped with bearer rings to provide constant adjustment forces between the form and transfer cylinders. In printing group cylinders which use printing-form sleeves or transfer-form sleeves, bearer rings cannot be located on the side of the cylinder on which the sleeve is either removed or slidably inserted. In order to obtain good printing results with cylinders of this type, great demands are placed on the cylinder bearings, particularly with respect to eliminating play of the cylinders. This is also true for the wall bushings which hold the cylinder bearings. However, these wall bushings are usually mounted on a side wall of the machine and have some degree of play. This is because it must be possible to turn the bushings in certain circumstances, as for example to enter either a print engagement or disengagement setting. It may also be necessary for the wall bushings to be movable.
It would therefore be desirable to provide a web-fed rotary printing machine which is able to obtain a good print quality while eliminating play on the part of the cylinders and allowing the bushings to be movable. It would also be desirable to provide such a web-fed rotary printing machine wherein a sleeve of the cylinder may be replaced while the cylinder maintains its position.